Process for producing heat-expandable microspheres and application thereof

Abstract

A process for producing heat-expandable microspheres which enables constant and high-yield production of heat-expandable microspheres having a mean particle size ranging from 0.01 to 10 μm without deteriorating their expansion performance, and the application thereof. The process produces heat-expandable microspheres containing a thermoplastic resin shell and the blowing agent encapsulated therein. The process includes a step of dispersing a polymerizable component and the blowing agent in an aqueous dispersion medium containing a polyester amide having an acid value (mgKOH/g) ranging from 95 to 140 and a step of polymerizing the polymerizable component.

The invention claimed is: 
     
       1. A process for producing heat-expandable microspheres comprising a thermoplastic resin shell and a blowing agent encapsulated therein, the process comprising dispersing a polymerizable component and the blowing agent in an aqueous dispersion medium containing a polyester amide having an acid value (mgKOH/g) ranging from 95 to 140 and polymerizing the polymerizable component, wherein the heat-expandable microspheres have a mean particle size ranging from 0.01 to 10 μm. 
     
     
       2. The process for producing the heat-expandable microspheres as claimed in  claim 1 , wherein the polyester amide is obtained from reaction of a carboxylic acid having at least two carboxyl groups and an amino alcohol having at least one amino group and two hydroxyl groups. 
     
     
       3. The process for producing the heat-expandable microspheres as claimed in  claim 1 , wherein the polyester amide has an amine value (mgKOH/g) ranging from 20 to 60. 
     
     
       4. The process for producing the heat-expandable microspheres as claimed in  claim 1 , wherein the amount of the polyester amide in the aqueous dispersion medium ranges from 0.0001 to 5 parts by weight to 100 parts by weight of the total of the polymerizable component and blowing agent. 
     
     
       5. The process for producing the heat-expandable microspheres as claimed in  claim 1 , wherein the carboxylic acid having at least two carboxylic groups is adipic acid, and the amino alcohol having at least one amino group and two hydroxyl groups is diethanolamine. 
     
     
       6. The process for producing the heat-expandable microspheres as claimed in  claim 1 , wherein the aqueous dispersion medium further contains a particulate metal compound having a mean particle size ranging from 1.0 to 20 nm. 
     
     
       7. The process for producing the heat-expandable microspheres as claimed in  claim 6 , wherein the particulate metal compound comprises colloidal silica and the pH of the aqueous dispersion medium is 7 or lower. 
     
     
       8. Hollow particles manufactured by thermally expanding the heat-expandable microspheres produced in the process as claimed in  claim 1 . 
     
     
       9. The hollow particles as claimed in  claim 8 , further containing fine particles coating an outer surface of the fine particles. 
     
     
       10. A composition containing a base component and the heat-expandable microspheres produced in the process for producing heat expandable microspheres as claimed in  claim 1 . 
     
     
       11. A formed product manufactured by forming the composition as claimed in  claim 10 . 
     
     
       12. A composition containing a base component and the hollow particles as claimed in  claim 8 . 
     
     
       13. A formed product manufactured by forming the composition as claimed in  claim 12 . 
     
     
       14. A formed product manufactured by forming the composition as claimed in  claim 9 . 
     
     
       15. A formed product manufactured by forming the composition as claimed in  claim 14 . 
     
     
       16. The process for producing the heat-expandable microspheres as claimed in  claim 1 , wherein the polyester amide has an acid value (mgKOH/g) ranging from 96 to 140. 
     
     
       17. The process for producing the heat-expandable microspheres as claimed in  claim 1 , wherein the polyester amide has an acid value (mgKOH/g) ranging from 99 to 140.